#include <iostream>
#include <vector>
using namespace std;
class Solution {
public:
    void reverseString(vector<char>& s) {
        int left=0,right=s.size()-1;
        while(left<right){
            swap(s[left],s[right]);
            left++;
            right--;
        }
    }
};
int main(){
    vector<char> s={'h','e','l','l','o'};
    Solution solution;
    solution.reverseString(s);
    for(auto s1:s){
        cout<<s1<<",";
    }
}